Telephone-exchange system



c. L. GOODRUM Filed April 17, 1920 TELEPHONE EXCHANGE SY S TEM Patented Apr. 17, 1923.

re srarss PATENT orrien.

CHARLES L. 'eoonno c, or nnwvonx, it. Y., ASSIGNOR r0 WESTERN ELECTRIC,

COMPANY, INCORPORATED, or new YORK, N. Y., A CORPORATION or NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed April 17, 1920. Serial No. 374,534.

To all whom it may concem. Be it known that 1, CHARLES L. GroonRUM a citizen of the United States, residing at New York, in the county of New York, State of .New York, have invented certain new and useful Improvements in Telephone Exchange Systems, of whlch the following is a full, clear, concise, and exact descriptlon.

This invention relates to improvements in telephone exchange systems, and has particular reference to systems employing machine switching in the completion ofconnections.

There have heretofore been provided in sush systems, selector switches which might.

be directively operated to associate an incoming line with one of a plurality of groups of outgoing lines, thereafter operating in a hunting movement to connect said incoming line to an idle line in the selected group. It has also been proposed to divide -such groups of outgoing lines into subgroups of equivalent trunks, means, such as a group contact, being provided ,totest the idle or busy condition of each sub-group in a single operation. With such an arrangement, if all the lines in the firstlsub-group were busythe incoming line would be successively associated with other sub-groups until a sub-group which contained an idle line was t'ound, whereupon the lines in this sub-group would be tested and the incoming line connected to the first idle line encouut ered. It is obvious that even by subdividing the outgoing lines into equivaleutsubgroups, there would stillybe a loss of time in establishing a connection while busy subgroups were being tested.

An object of the present invention is to avoid the delayoccasionedin testing terminals of groups'in which all trunks are busy by preselecting a group containing an idle trunk and causing the selector to immedi I has its terminal bank divided into groups G, to the ter 'nnals'of which are connected the trunks to which said selector has access. Each group of terminals is di vided into a plurality of rows or subgroups equal in number to the largest digit employed to operatesaid selector to select an idle trunk. various main groups are divided into sub groups of equivalent trunks and, as will ap pear in the course of the description, as long as there is an idle trunk in a subgroup of equivalent trunks in group G, the selector will operate tosele'ct said idle trunk." When all the equivalent trunks of a subgroup are bus-y, the selection of an idle trunk is switched to the next main group containing a subgroup in which an equivalent trunk is idle. Each subgroup is shown as comprising ten sets of trunk terminals to which an equal number of trunks are connected. In order to avoid confusion, the drawing illustrates only a few of the equivalent" trunks. Thus for the main group G, three of the ten equivalent trunks assigned to the third level or subgroup are shown, one of the trunks being connected to the fourth set' o terminals in'said subgroup. Similarly in group G, three trunks, which are the equiva lent of those just mentioned, are shown as assigned to the third .level or subgroup Each trunk has a relay 1 individual thereto which may be operated in any well-known manner when the. trunk is taken. for use Should one or more trunk-s in a subgroup in group G be idle, its corresponding relay maintained energized through the contacts of the 'deenergized relays 1. When all the "truuks'in said subgroup are busy, a circuit for relay 2, w ll no longer be maintained since all of the relays 1 will be energized and relay 2 will. therefore, release and close a circuit through'itslower contact for a similar relay 2, common to the subgroup of the trunks in group G which are equivalent to the first named subgroup. If a trunk in the second subgroup is idle, the circuit for relay 2' will becompleted through the contact of the relay 1 individual to said idle trunk, and rela v 2- will be energized. Relays 2, 2, and

other similar relays each control a brush' tripping rod 3 which, when its associated relay is energized, has its trips 4: in operative position, as shown man lines in Figs. 2 and It will thus be apparent that relays 2,

Likewise, the trunks in the will be deenergized.

2, etc, operate to 'preselect from the various subgroups of equivalent trunks, the first subgroup in which an idle trunk is to be found.

Each of the selectors S and S includes a shaft 5 carrying a number of brush sets 6 and 6 equal to the number of main groups G, G, etc. The brushes of each-set are normally spaced by insulated Spreaders 7, pivoted in a frameS, and having an extension or lever 9, which contacts with a trip t when the latter is in its operative position, as shown in full lines in Fig. 2, as soon as the selector starts its secondary or trunk hunt ing movement. The spreader-s 7' are thus moved from engagement with the brushes to the dotted line position shown in Fig. 2, and the brushes are permitted to engage the terminals of the subgroup of trunks in which the idle trunk is located, whereupon the trunk hunting movement of the selector proceeds as usual. In order that the brushes maybe restored to their normal positions upon the release of the selector, an abutment is arranged in the path of the lever 9 and is contacted thereby as the selector is returned to normal whereby said lever is again moved to its full line position in Fig. 2 and the Spreaders 7 engaged with said brushes to separate the same.

Itis believed that the invention will now be fully understood from the following detailed description of the operation in extend ing a connection. Let it be assumed that a subscriber at substation A desires to extend a call and that the first digit of the desired number is 3. Let it further be assumed for the moment that there are one or more idle trunks located in the subgroup of equivalent trunks terminating in the third level of the main group G, and that the first of said idle.

trunks is connected to the fourth set of terminals in said subgroup. In thls instance the relay 1, individual to said fourth trunk,

and similar relays of any other idle trunks, A circuit will then be established for the common relay 2 extending from grounded battery through the winding of said relay, and the contact of relay l of the fourth trunk to ground. Relay 2, in energizing, rotates the trip. rod 3associated therewith to move the trips 4 to operative position and at the same time opens the lower or normal contact of the relay to,

prevent'energization of the relay 2 or other ,similar relays. It will thus be obvious that the tripping rods ,3 associated with relay 2' and the other similar relays will be prevented from being moved to, thelr operative positions, and'consequently the first subgroup of equivalent trunks containing an idle one will be preselected.

. Upon the removal of the receiver from the switchhook at substation A, a. circuit is immediately established to operate a line finder B or other switch of well-known construction, and upon engagement of the brushes of said switch with the terminals of the calling line, a circuit will be established for the line relay 10 of the selector S extending from grounded battery through the right-hand winding of said relay, the wiper 11 in posi tion 1, brush 12, terminal 13, substation apparatus, terminal 14, brush 15, wiper 16 in position 1, and left-hand winding of relay 10 to ground. Relay 10 energizes and estabits front contact a circuit for the slow-to-release relay 17, which, in turn, prepares at its front contact a circuit for the slowtorelease relay 18. The subscriber now operates his impulse sender and proceeding under the assumption that the first digit of the wanted number is 3, three impulses are transmitted. The first interruption of the circuit of line relay 10, due to the first impulse transmitted, causes said relay to release its armature and establish the circuit for relay 18, which then energizes. Relays 17 and 18, being slow to release, maintain their front contacts closed during the transmission of the impulses. Energization of relay 18 establishes a circuit for escape magnet 19 through the wiper 20 in position 1, but the escape mechanism controlled by magnet 19 is so arranged that the Wipers thereof will not be moved into position 2 until the magnet releases. Each closure of the back contact of relay 10, in response to the impulses transmitted, establishes a circuit for the primary stepping magnet '21 of the selector, extending from grounded battery through the winding of said magnet, rotary off-normal contact 22, front contact of relay 17, and the back contact of relay 10 to ground. Magnet 21 responds to each closure of the circuit therefor and operatesto step the shaft 5 of the selector in its primary or vertical movement. In response to the three impulses transmitted, the sets of brushes 6, 6', etc, will be moved to positions opposite the third subgroups of equivalent trunks in the various corresponding main groups Gr, G, etc. Inasmuch as the lower or front contact of relay 2 is opened, it will be apparent that the tripping rod 3, associated with the third subgroup in group. G and other similar trip rods of the other main groups, will be in normal or inoperative position so that the brush set 6 and the remaining brush sets associated with the other main groups will not be affected during the secondary or hunting movement of the selector. At the end of the primary movement, the lever 9 of brush set 6 will be.

disposed so as to contact the adjacent trip 4 carried by the tripping rod 3 of group G as soon as the selector begins its trunk hunting movement. At the termination of the transmission of the impulses relay 18, after an interval, releases and opens the circuit for escape magnet 19, which then releases to move its wipers into theirsecond positions.

. A self-interrupting circuit for the secondary magnet 23 is then established, extending from grounded battery through the winding of said magnet, contact 24-, wiper in position 2, and the front contact of relay 10 to ground. Magnet 2-3 operatesto rotate the shaft 5 of the switclnand upon the first step thereol in its secondary movement, the

oil-normal contact 22 is opened. The initial movement of the shaft causes lever 9 of brush set 6 to be'roc-lred about its pivot and the spreader-s 7 to be disengaged from the :the test terminal of the idle trunk to ground at the succeeding selector. In this instance the onergization. oi the escape magnet over the circuit usttraced causes the side SWltCli to move its wipers into position 3, whereupon thestepping circuit for the secondary magnet 23 is permanently opened and the selector comes to rest on the terminals of the idle trunk. llpon the seizure of the idle trunk, the round potential at the. succeed D ing'selector is removed in any manner well knownin the art, and acircuit (not shown) is established font-he relay 1 individual to the seized trunk. Relay 1 energizes and opens its contact to preventithe establishment of a circuit for the magnetfl through said cont-act while the trunk is. being used. It will thus be seen that it allot the trunks inthe third subgroup are taken for use, the

associated relays 1 will all be energized and a circuit will no longer be maintained for whereupon ,the same will release rela y 9,,

contact to and. in doing so, close its lower establish a circuit for relay associated 3 with. the third. subgroup in group G, should anyof the individual relays assigned to said group be iii-normal position;

It at any time-during the primary or secondary movement of? the selector, a subscriberat A should replace his receiver upon .batterv throunhthe w] theswitchhook; relay ill will immediately deenergii-ce and open the circuit forrelay 17, which, after an interval, will release.

lease'magnet 26., extending from grounded the oil-normal; contact 27, which is closed upon the first vertical, step'ot' the switch shat't 5, the side switch wiper 28 ill POSl A 'circnit .will' then'be established. for the re .rling ofsaidmagnet,

tions 1 or 2,,and. the back contacts of relays x1? and 10 to ground. Magnet 26 will energize and lock up through the oft-normal contact 27 and the contact 29 until the selector has been restored to normal, whereupon the off-normal contact 27 will again be opened to breakthe locking circuit for said magnet. I i

hen theselector S is operated to seize the idle trunk, as above described, and the side switch wipers have been moved into their third positions, the subscribers line will be extended through wipers 11 and 16 and the uppermost brushes of brush set 6 to the trunk leading to the next succeeding selector, which may be constructed similarly to the one shown in the drawing. Succeeding impulses transmitted from substation A will operate the succeeding selectors in a man ner which will be clearly understood. a

At the termination of the conversation, the selector succeeding selector S releases andl'again connects ground to the test conductor of the seized trunk, and at the same time opens the energizing circuit of the relay 1 individual to said trunk, which then releases, Placing of ground upon the conductor of said trunk establishes an energizing circuit for the release magnet 26 over "the path previously desc ibed to the sine switch wiper 2S inits third position, and from thence through the lowermost brush of the brush 6. Magnet 26 energizes and locks up, as

previously described, and the selector S is thereupon restored to normal. Upon the restoration of the selector to its normal position, lever 9 o-fbrush set 6, which is in the operated position shown in dotted lines in Fig. 2, contacts the abutment 10 and is thereby restored; to itsnormal position with the Spreaders 7 in engagement with the intermediate brushes oi the set, thus restoring said brushes-to normal. The line finder ,B is also restored in a well-known manner and the apparatus is-again ready for the extension of another call.

What is claimed is:

1. In a telephone system, a sender. a selector, a plurality of trunks terminating in said selector and arranged in equivalent sub groups, means for preselecting a subgroup containing anidle trunk, and means including said sender for operating said selector to select saididle trunk. 2. In a telephone system, a selector, sender, groups of trunks terminating in said selector and comprising subgroups of equivalent trunks, means for preselecting a sub-- group containing an idle trunk, and means includin said sender for operating said selector to select said idle trunk.

3. In a telephone system, a selector, a sender, groups of trunks terminating in said selector and comprising subgroups of equivalent trunks, sets of brushes for said selector,

the brushes of which are normally in inoperative relation to the terminals of said trunks, means for preselecting a subgroup in which an idle trunk is located, means ineludingsaid sender for operating said seleetor, and means for actuating a set of brushes to contactthe terminals of the sub group containing the idle trunk.

4e In a telephone system, a selector having primary and secondary movements, a sender, groups of trunks terminating in said selector and comprising; subgroups of equivalent trunks, sets of brushes for said selector, the brushes of which are normally in inoperative relation to the terminals of said trunks, means for preselecting" a subgroup containing an idle trunk, means including said sender for operating said selector, and means for actuating a set of brushes at the beginning of the secondary movement of said selector to contact the terminals of the subgroup containing the idle trunk.

5. In a telephone system, a selector, a sender, a plurality of trunks terminating in said selector and arranged in equivalent subgroups, switching means for determining the condition of the trunks in each subgroup, means controlled by said switching means for prcselecting a subgroup of the equivalent trunks containing an idle one, and means including said sender for operating the selector to select an idle trunk in the preselected subgroup.

6. In a telephone system, a selector, a sender, a plurality of trunks terminating in said selector and arranged in equivalent subgroups, switching means common to the trunks of each subgroup, for determining the condition of the trunks therein, means common to the trunks of each subgroup and controlled by said switching means for pre selecting a subgroup containing an idle trunk, and means including said sender tor operating said selector to select the idle trunk in the preselected group.

7. In a telephone system, a sender, a selector having primary and'secondary move ments, means including said sender for operating said selector, groups of trunks terminating in said selector and comprising subgroups of equivalent trunks, switching means for determining; the condition of the trunks in each subgroup, means controlled by said switching means for preselectingg a subgroup of the equivalent trunks containinnan idle one. sets of brushes for said selector normally in inoperative relation to the terminals of the trunks. and means operable at the beginning of the secondary movement of the selector tor actuating a set of brushes to contact the terminals of the preselected subgroup containing the idle trunk.

trunk, and means operable at the beginning of the secondary movement of said selector for actuating a set of said brushes to contact the terminals of the preselected subgroup containing the idle trunk.

9. In a machine switching telephone system, a selector, a plurality of equivalent trunks terminating in said selector in a number of levels, a brush on said selector for each level, a sender for positioning said selector with a brush opposite each of said levels, said brushes being normally in inoperative relation to the' terminals of said trunks, means for giving said selector an automatic secondary movement, means actuated in the beginning of the secondary movement of the selector for rendering, operative the brush of a level containing an idle trunk, and means for causing said brush to seize said idle trunk.

10. In a machine switching telephone exchange system, a selector, subgroups of equivalent trunks terminating therein, a

' brush on said selector for each subgroup, a

sender for positioning the selector with its brushes at the beginning of said subgroups, means common to each subgroup for render ingr operative the brush oi a subgroup having an idle trunk, means for imparting an automatic secondary movement to said sclector. and means for causing said brush to seize said trunk.

11. In a machine switching telephone exchange systennfa numerical selector, a number of trunks terminating in said selector and arranged in equivalent subgroups, a brush on said selector for each subgroup, a sender for giving said selector a primary movement to set its brushes in operative relation to the desired subgroups, means thereupon automatically operated for giving said selector a secondary movement over said subgroups, means actuated in the initial part of said secondary movement for rendering operative the brushof a subgroup containing an idle trunk, and means for causing said brush to seize said trunk.

In witness whereof, I hereunto subscribe my name this 16th day of April, A. D., 1920.

CHARLES L. GOODRUM 

